Why first symbol only have half number of sample in Modulation toolkits

[MarcoKwok]

I am using Labview 8.6 with Modulation toolkits 4.0 on windows XP for ASK signal generation.

This one is the output with 1 bit as input.

This one is 2bit input.

It is suppose that the output size should be 16 for 1bit and 32(16+16) for 2 bits , but now it is 8 for first bit and 16 for the second.

Clearly the period of first bit is shorter than the second.

Why is that?  I will use the output of this program for NI5671 AWG, would it cause any problem to generate the original pattern?

best,

Marco Kwok

[Doug_L._Bear]

Is this occuring on the RFSG side of things or on the RFSA side of thigns.  That is, are these graphs showing the data coming out of the modulation VI in the generation portion or are these graphs showing data acquired with a 5661?

If it is the second case it could just be that your 5661 is not triggering fast enough to acquire all the samples, try changing the reference trigger position to see if you can acquire pretrigger samples that show before the first bit.  You can also put a graph on the generation side of things after the IQ data is formed to see if that is done correctly.